Development of a material model for predicting extreme deformation and grain refinement during cold spraying
Development of a material model for predicting extreme deformation and grain refinement during cold spraying
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DOI：
10.1016/j.actamat.2020.08.052
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发表时间：
2020-10
期刊：
影响因子：
9.4
通讯作者：
Qian Wang;N. Ma;M. Takahashi;Xiao-Tao Luo;Chang-jiu Li
中科院分区：
文献类型：
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作者：
Qian Wang;N. Ma;M. Takahashi;Xiao-Tao Luo;Chang-jiu Li
基于熔融的增材制造技术（例如选择性激光熔化、电子束自由成形制造）引起凝固问题，例如晶粒粗糙度和高孔隙率。冷喷涂技术作为一种新的技术，可以克服这些缺陷。在这项研究中，使用位错动力学的材料模型是专门为CS过程描述以下五个纳秒级的物理现象：应变硬化，正常范围的应变速率硬化，超高应变速率硬化，热软化和晶粒尺寸的演变。一个单一的铜微粒的冲击试验进行，并观察到实验和模型预测的微粒变形之间的良好协议，表明高模型的准确性。建立了相应的有限元模型，详细讨论了上述现象的个别影响，表明材料变形主要受超高应变率硬化控制，而喷射主要受热软化控制。此外，模拟和实际的晶粒尺寸分布表明，晶粒细化只发生在附近的微粒-基板界面（主要是在界面边缘）。因此，新开发的模型可以准确地再现冲击颗粒的动态变形行为，并正确地预测晶粒细化（特别是由于动态再结晶）。
Fusion-based additive manufacturing techniques such as selective laser melting, electron beam freeform fabrication cause solidification problems such as grain coarseness and high porosity. As a new technique, cold spraying (CS) can overcome such melting-induced drawbacks. In this study, a material model using dislocation dynamics was developed specifically for the CS process for describing the following five nanosecond-scale physical phenomena: strain hardening, normal-range strain rate hardening, ultra-high strain rate hardening, thermal softening and grain size evolution. A single Cu microparticle impact test was conducted, and a good agreement between experimental and model-predicted microparticle deformations was observed, indicating high model accuracy. The corresponding finite element model was established, and the individual effects of the above phenomena were discussed in detail to show that material deformation is mainly controlled by ultra-high strain rate hardening while jetting is controlled by thermal softening. Additionally, both simulated and actual grain size distributions indicated that grain refinement occurs only near the microparticle-substrate interface (mainly at the interface edge). Thus, the newly developed model could accurately reproduce the dynamic deformation behaviors of impacting particles and correctly predict grain refinement (particularly due to dynamic recrystallization).